Structured spin angular momentum in highly focused cylindrical vector vortex beams for optical manipulation.

We investigate the spin properties of a family of cylindrical vector vortex beams under a focusing condition. The spin-orbit interaction is demonstrated by comparing the energy flow and spin flow density of the focused field to those of the incident field. This spin-orbit interaction is analyzed to construct the desired distribution of spin angular momentum for optical manipulation. The structured spin angular momentum of the focused field can transfer to the optical torque for the non-magnetic absorptive particle. The influences of polarization topological charge, vortex topological charge and wavelength on optical torque in the hot-spot of focused field are summarized for three typical particles. Such results may be exploited in practical optical manipulation, particularly for optically induced rotations.